Pretty easy. If its already in a vial, then just add 5cc's of bac water and use a 1cc slin pin. Every 1cc on the slin pin is 1000iu, so 400iu's would be 4units on the 10unit slin pin. If the 5000 is in an amp, but a cheap $1 10ml emply sterile sealed vial. Add 4cc's bac water in it. Then break the amp and gently let 1cc bac water slide down the side of it. Swirl it around a little and make sure all the powder dissolved, then suck the 1cc back up and add to the vial.